It can be anything! An apex, subdomain, or even a URL.

Results forwebdisk.etheroom.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2017-09-16T18:45:56.478	2017-09-13T00:00:00	2017-12-12T23:59:59	etheroom.com	webdisk.etheroom.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2017-07-17T18:35:57.381	2017-06-29T00:00:00	2017-09-27T23:59:59	etheroom.com	webdisk.etheroom.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"
2017-05-27T18:30:19.37	2017-04-14T00:00:00	2017-07-13T23:59:59	etheroom.com	webdisk.etheroom.com	C=US, ST=TX, L=Houston, O="cPanel, Inc.", CN="cPanel, Inc. Certification Authority"